Metal spraying method



July 8, 1947. R. ERHARDT METAL SPRAYING METHOD Filed May 20 1944 INVEN TOR. BY Rz'dzarzzEr/zardi flTTORNEY Patented July 8, 1947 UNITED STATES PATENT OFFICE Claims.

This invention relates to a method and apparatus for spraying molten metal to improve the character of the metaldeposit made by such a process.

For the application of molten metal sprays several devices have been developed and used which involve the feeding of a wire of the metal to be deposited through the gun and bringing to a focus on the wire at a melting zone streams of fuel gas, usually acetylene and oxygen adequate to melt the meter together with a carrier stream of air at higher pressure to form a spray of the molten metal which may be projected against the body to be coated. Such deraces are capable of melting and spraying steel, copper, bronzes, brasses, aluminum, zinc, lead, tin, cadmium, and other metals.

@'ne qf such devices is disclosed in U. S. Patent 1,776,632, and is currently sold under the name eithe Metal Spray Company of LOs Angeles. In this device the metal wire is fed from the back of the gun but through the nozzle and at a point or, zone slightly beyond the end of the lnozzle the melting of the wire takes place from the heat supplied by the combustion of the hcetylhe and oxygen. The acetylene is usually suiYplied to the gun at a pressure of about lbs. for the above mentioned metalswith the exception of lead and tin, while for these two metals a pressure of 11 lbs. is usually adequate. The oxygen is usually supplied to the gun at a pressure of about 12 lbs. for the lead and tin and at about 1'7 lbs. forthe other metals. The. carrier stream of air fed through the gun and more or less mixed, with the oxygen or acetylene within the gun is usually supplied at about 50 to 60 lbs. pressure.

I have discovered that by applying to the molten metal spray beginning at a point slightly beyond the melting zo'ne an enclosing sheath of hydrogen supplied at relatively low pressure, for example, 1 to 5 lbs, a substantial reduction in oxidation of the metal while it is in molten condition is accomplished, and the character of the grain of the deposited metal is greatly improved.

Accordingly, one of the objects of this invention is to supply such a sheath of hydrogen in the manner described to a molten metal spray being-formed and projected in the manner above described.

Another object 'of the invention is to provide an apparatus by means of which such a sheath of hydrogen may be applied without disturbing the normal lightning and operation of the metal spray gun, while improving the metal depositing results obtained thereby.

Further particular objects and advantages of the invention will become apparent from a perusal of this specification.

Referring now to the drawing,

Fig. 1 is a perspective view showing, for illustrative purposes, a type of metal spraying gun utilized in performing my invention.

Fig. 2 is a detail view, partly in section, showing one form of the attachment which I add to such a gun for carrying out my invention.

means, usually an air driven turbine motivated mechanism for continuously feeding the wire from the back of the gun out through its nozzle, ducts including regulating valves for supplying a gas such as acetylene and another gas such as oxygen to the interior of the gun, s that they may be projected out through the nozzle surrounding the wire with the purpose of having the combustion take place in the atmosphere just beyond the nozzle where the wire will be melted.

. Such devices include provisions for supplying air at higher pressure to the interior-of the gun and ejecting it'along with the fuel gases to form a carrierstream for the molten metal capable of projecting it in atomized form against the body to be coated. The details of construction of'such guns do not constitute part of this invention, as they are already well-known in this art. r

As indicated above, my invention comprises adding to such guns means for applying an enclosing sheath of hydrogen gas to the atomized metal spray just slightly beyond the melting zone, and in furtherance of that object I provide, as shown in Figs. 2 and 3, an attachment for the gun comprising a manifold I having an annular channel 2 into which hydrogen is fed by means of the pipe 3. The manifold may be secured in any suitable manner to the gun i. For example, the exterior of the nozzle 5 may be provided with threads, as shown at E, and by means of corresponding threads on the manifold the latter may be secured in position. In the form of construction shown, an annular plate I may be utilized to 'seal off one side of the manifold channel, as shown in Fig. '2, and a gasket 8 may be supplied additionally for effecting this seal, the gasket being pressed against the face 9 of the housingof the gun. At separated apart intervals, surrounding the nozzle a number of jets such as I I, each having a duct I2 may be'secured in any suitable manner, for example, as shown, to the manifold for conducting .theihy drogen gas forwardly toward the end of the nozzle. I have found that four jets are adequate for the usual gun, although a greater or lesser number may be used, if desired. The control valves for. regulatingthe fuel gases, the airand the hydrogen are not shown, as they do not constitute a part of the invention.

In the operation of the gun with the improvement shown in Figs. 2 and 3 attached thereto, after the gun has been ignited,.that-.is=.by igniting the acetylene and oxygen, the. air stream will be admitted to the gun and as the wire is" fed forwardly, usually automatically; the: metal wire will melt just beyond the end of the nozzle. and the molten metal willbe carried in spray "form by the air stream. The hydrogen may then be turned on, and as it fiows,-under low pressure, that is, about 1 to 5110s. pressure; it-will envelop the stream of air, molten metal, and products of combustion, and will be ignited by its contact with the metal spray. Theoxygen required to support the combustion of the hydrogen may be derived either from the oxygen found Within the metal spray or from the atmosphere through which the metal spray fiows.

I have found that when the invention is used in the manner described, the deposited metal will have a characterand color considerably different from that which would be deposited without the use of the hydrogen. It will, in the case of any of the above-mentioned metals, have a color more closel approximating the color-of the same meta-1 produced either by casting orforging processes. Also, the grain or texture of the "deposited metal will in all cases be'finer, more dense, and, in the case of the hard metals, will be harder than can be obtained without the use of the "hydrogen supply. Also, the bonding of the metal coating upon the article being coated-ia'Ifind, more firm and more permanent.

One of the advantages noted in metal coatings deposited in accordance withthis invention resides in the fact that the deposited layers of metal aresuited better'for-machining or grinding operations.

A modified form of the improveda'ttachment is shown in Figs. 4 and -5. In this case the distributor for the hydrogen provides a circular orifice'rather than aplurality ofjets. "To "accomplish this, a member I3 is attached to the nozzle of the gun, for example, by 'the' threa'ds showmand a shield I4 is secured thereto, for example, by the threads shown, thus providingamanifold channel l5 and a hydrogen supply passage '16 which extends around the nozzle '5.as-shown. The hydrogen emitted from the circular orificewill then flow along the outside surface of the'nozzle and form an-enclosing sheath wholly surrounding the atomized metalspray, being ignitedand burned in the same manner as wasdescribed above in connection with Fig. -2. 'Atgasket I! may be employed, as shown, to aid the sealing'of the'manifold channel I 5.

In the operation of either device,.as.the wire l8 emerges beyond'the end-.of the nozzle,"-itis subjected to the heat supplied. in't-hat'zone by the combustion of the oxygen :and the acetylene. This region, where thewire-passes from solid to molten state, is referred to as the melting zone. As the metal melts, it is blown off the end of the wire in finely divided particles by the action of the carrier stream of air,-which is usuallysupplied to the gun at about 60lbs. pressure. Lower pressures such as 11 to 17 lbs.areusually-adeuuate for the fuel gases.

One effect which appears to take place, :in

gen in thesurroundingatmosphere from making ."contact with the molten metal, particularly while it is at its highest temperatures, and apparently diminishes the amount of oxygen in the carrier stream.

The reduction in oxidation of the metal spray resulting from lessened contact of the molten metal with oxygen appears to contribute to the finenessgdensity' and improved machining charit is supplied'at low pressure, preferably'inthe range indicated. Even'less than "1 lb. may be used, but it does not appear'advantageous'to'use pressures much in excess of 5 lbs. At these low pressures the rate of flame propagation ba'ck toward the hydrogen orifice or orifices'is fast enough So that the hydrogen is-already' burning when it strikes the conical spray of"atomized metal.

For the purpose of illustrating convenient modes of utilizing this invention I have shown in some detail attachments for supplying the hydrogen, but it will be recognized thatthese attachments may be varied 'and'otherwise constructed, without departing from the principles of the invention herein described.

Having shown and described 'my"invention, "I claim:

' 1. The methodof'sprayin'g molten metal, which comprises feeding the metal to be meltedito a melting zone, supplying oxygen and a hydrocarbon .gas at'moderate pressures to the melting zone for melting the material, supplying a carrier stream of airto the melting zone at apressure and velocity exceedingthose of thefuel gases, and

, circumferentially' blanketing the, projected spray stream beyond the melting zone with a sheath of hydrogen added thereto at low, pressure andvelocity in a directionsubstantially. parallel to the flowingspray stream in the. open atmosphere beyond the confines of theapparatus employed. in

. pro ecting the spray stream.

. 2. The method of spraying molten metal, which comprises feeding the metal to bemelted to a melting .zone, supplying. oxygen and a -hydrocarbon' gas to themeltingzone for melting the material, supplying a carrier stream of airlformix- ,ing with the molten metal andcombustiblegases,

and circumferentially enclosing the projected pray of metal, and gases with a sheathof hydrogen applied to said spray in-a" direction substantially parallelto the flowing spraystreamin the open atmosphere beyond the confines of the apparatus employed in projectingthe. spray stream at a pressure and velocity less than halfthose of the fuel gases.

3. The method ofsprayingmoltenmetal comprising continuousl-y feeding-the metalto'a melting zone, supplyinga hydrocarbongas and oxygen to the melting zone for melting the metaLtsuppIying to the-melting zonea carrier =stream of air atpressures'and velocities greatly-exceeding those of. the fuel gases for projecting asprayofmelted metal, and applying a circumferential sheath contacting the metal spray consisting of hydrogen gas supplied in a direction:substantiallyparvallel to the flowing spray streamcircumferentially to r the spray in the open atmosphere beyond the confines of the apparatus :employedin projecting the spray streamat a pressure andivelocity much lower than those of the fuel gases and beginning at a zone beyond the melting zone.

4. The method of spraying molten metal comprising continuously feeding a metal wire to a melting zone, supplying acetylene and oxygen to the melting zone at pressures ranging between and 17 lbs. for melting the wire, supplying air at about 60 lbs. pressure to the melting zone to atomize and project the melted metal, and enclosing the projected spray of metal and gases beginning at a point .beyond the melting zone in the open atmosphere beyond the confines of the apparatus employed in projecting the spray stream with a sheath of hydrogen gas added thereto at pressures under 5 lbs. in a direction substantially parallel to the flowing spray stream.

5. The method of spraying molten metal which comprises feeding a metal wire to a melting zone, mixing oxygen and acetylene at a medium pressure and projecting them out into the atmosphere and burning them at said melting zone where the wire is thus melted, projecting along with the oxygen and acetylene a, stream of air at much higher pressure to atomize the molten metal and project it onto the object being coated, and sup- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,262,134 Stolle Apr. 9, 1918 1,617,166 Schoo Feb. 8, 1927 1,843,842 Schoop Feb. 2, 1932 1,776,632 Lensch et al Sept. 23, 1930 1,930,373 Stubenrauch Oct. 10, 1933 20 2,231,247 Bleakley Feb. 11, 1941 2,092,159 Bleakley ,Sept. 7, 1937 2,317,173 Bleakley Apr. 20, 1943 FOREIGN PATENTS Number Country Date 548,630 Great Britain Oct. 19, 1942 plying to the outside of the metal spray a circum- 

